Reactions of molecular oxygen with oxidisable reactants in the presence of fluidised beds of catalyst are known. For example, the acetoxylation of ethylene to produce vinyl acetate by reaction of acetic acid, ethylene and an oxygen-containing gas in a fluid bed reactor is known from EP-A-0672453, EP-A-0685449 and EP-A-0847982. The reaction of oxygen with ethane to produce acetic acid in a fluid bed reactor is known from EP-A-0546677.
EP-A-0685449 discloses a process for manufacturing vinyl acetate in a fluid bed reactor comprising feeding ethylene and acetic acid into the fluid bed reactor through one or more inlets, feeding an oxygen-containing gas into the fluid bed reactor through at least one further inlet, co-joining the oxygen-containing gas, ethylene and acetic acid in the fluid bed reactor while in contact with a fluid bed catalyst material to enable the ethylene, acetic acid and oxygen to react to produce vinyl acetate and recovering the vinyl acetate from the fluid bed reactor. According to EP-A-0685449, the oxygen may be added in pure form or as an admixture with inert gas such as nitrogen or carbon dioxide. Since the oxygen and hydrocarbons are not mixed until they are both inside the reactor, catalyst is present when they meet and reaction proceeds immediately, causing the oxygen partial pressure to drop. Thus, an advantage of feeding an oxygen-containing gas to the reactor through at least one further inlet in addition to the ethylene and acetic acid reactants is that it allows significantly higher levels of oxygen to be safely employed without a high inventory of flammable gas mixtures.
Bubbling bed operation is not appropriate for reactions using molecular oxygen-containing gas because of the possibility of a plume or bubbles of oxygen forming in the bed, which can be unsafe.
There remains a need for an improved fluid bed process in which molecular oxygen is reacted with at least one oxidisable reactant.